Author: lwall
Date: 2010-03-07 15:42:59 +0100 (Sun, 07 Mar 2010)
New Revision: 29976
Modified:
docs/Perl6/Spec/S06-routines.pod
docs/Perl6/Spec/S12-objects.pod
Log:
[S06,S12] make attributive parameters default to 'is copy' binding
make easy way for an attribute to override this with 'is ref'
Modified: docs/Perl6/Spec/S06-routines.pod
===================================================================
--- docs/Perl6/Spec/S06-routines.pod 2010-03-07 13:53:10 UTC (rev 29975)
+++ docs/Perl6/Spec/S06-routines.pod 2010-03-07 14:42:59 UTC (rev 29976)
@@ -16,8 +16,8 @@
Created: 21 Mar 2003
- Last Modified: 9 Feb 2010
- Version: 128
+ Last Modified: 7 Mar 2010
+ Version: 129
This document summarizes Apocalypse 6, which covers subroutines and the
new type system.
@@ -1543,7 +1543,7 @@
submethod initialize($.name, $!age) {}
-then the argument is assigned directly to the object's attribute of the
+then the argument is bound directly to the object's attribute of the
same name. This avoids the frequent need to write code like:
submethod initialize($name, $age) {
@@ -1551,6 +1551,22 @@
$!age = $age;
}
+The initialization of attributes requires special care to preserve
+encapsulation; therefore the default for attributive parameters is
+value semantics, that is, as if specified with C<is copy>. Hence,
+the submethod above is really more like:
+
+ submethod initialize($name is copy, $age is copy) {
+ $.name := $name; # or maybe = here, since it's a parent's attr
+ $!age := $age; # or maybe only $! parameters work really
+ }
+
+If you wish to allow the user to initialize an attribute by reference,
+you may either write your own initializer submethod explicitly, or
+simply mark the attributes you want to work that way with C<is ref>:
+
+ has $!age is ref; # BUILD will automatically use ref binding, not copy
+
To rename an attribute parameter you can use the explicit pair form:
submethod initialize(:moniker($.name), :youth($!age)) {}
Modified: docs/Perl6/Spec/S12-objects.pod
===================================================================
--- docs/Perl6/Spec/S12-objects.pod 2010-03-07 13:53:10 UTC (rev 29975)
+++ docs/Perl6/Spec/S12-objects.pod 2010-03-07 14:42:59 UTC (rev 29976)
@@ -13,8 +13,8 @@
Created: 27 Oct 2004
- Last Modified: 24 Jan 2010
- Version: 98
+ Last Modified: 7 Mar 2010
+ Version: 99
=head1 Overview
@@ -796,9 +796,9 @@
is equivalent to
- submethod BUILD ($tail, $legs) {
- $!tail = $tail;
- $!legs = $legs;
+ submethod BUILD ($tail is copy, $legs is copy) {
+ $!tail := $tail;
+ $!legs := $legs;
}
Whether you write your own C<BUILD> or not, at the end of the C<BUILD>,
